The present invention relates to closed-caged carbon molecules known as Buckminsterfullerenes or fullerenes.
Fullerenes were first reported by Kroto et al. in carbon vapor produced by laser irradiation of graphite ((Nature 318, 162-164 (1985)). Fullerene C.sub.60 is a closed cage carbon structure containing 20 six-membered rings and 12 five-membered rings with the appearance of a soccer ball. There has been a surge of scientific interest in these compounds because they represent a new class of carbon in addition to the two known forms, graphite and diamond.
Fullerenes have many potential applications. The ability to intercalate metal cations into the structure suggests uses as catalysts in industrial processes. The potassium-fullerene C.sub.60 is a superconductor with a T.sub.c of 11K. The fullerene C.sub.60 surface is susceptible to chemical reactions such a hydrogenation and fluorination. Fluorinated fullerenes are expected to be good lubricants.
Full development of the utility of fullerenes has been hampered by the inability to produce macroscopic quantities of the material in an inexpensive, efficient process. Recently, C.sub.60 and C.sub.70 fullerenes have been produced in macroscopic quantities by graphite vaporization with resistive heating (Kratschmer et al. Nature 347, 354-358 (1990)). The formation of fullerenes in sooting flames is an appealing prospect since much data are available for these flames. It has been argued that the hydrogen present in sooting flames would favor the formation of aromatic structures known as polycyclic aromatic hydrocarbons (PAH) over fullerenes. Gerhardt et al. detected all-carbon ions having the same molecular weights as fullerenes in flames (Chem. Phys. Lett. 137, 306-310 (1989)). The presence of the neutral species in flames has not yet been definitively established.